Gastrointestinal stromal tumors: CT and MRI findings

Abstract

The objective of this study was to report the CT and MRI appearances of primary and metastatic gastrointestinal stromal tumor (GIST). The clinical and imaging findings of 31 patients with histological and immunohistochemical diagnosis of GIST were reviewed. The CT and MRI findings were assessed independently for size, location, enhancement characteristics, and pattern of metastatic disease. The tumors were of enteric (n=13), gastric (n=12), duodenal (n=2), and rectal (n=3) origin. In one case the primary site was the mesentery, without involvement of bowel. Primary tumors were typically exophytic (79%), larger than 5 cm (84%), and inhomogeneously enhancing (84%). Central necrosis of all tumors (37%) and aneurysmal dilation of enteric tumors (33%) were less common. Metastases were most commonly to mesentery (26%) or liver (32%). Less common findings were ascites (7%) and omental caking (3%). Liver metastases were hypervascular in 92% of patients and rapidly became cystic following therapy with imatinib mesylate (Gleevec; Novartis, East Hanover, NJ, USA). Lung metastases, bowel obstruction, vascular invasion, and significant lymphadenopathy were not seen in any patient. GISTs have some specific CT findings which could help differentiate them from other gastrointestinal tumors. Liver metastases became cystic following therapy, mimicking simple cysts. MRI was better than single-phase CT for assessing liver metastases, while CT was more sensitive for mesenteric metastases.

Tomographic Findings of Gastric Gastrointestinal Stromal Tumor and Correlation With the Mitotic Index

“…Many series do not present any case with this finding (3,22,29,30,32) , which is described in up to 2.5% of cases (16) . In our cases, we found one case presenting lymphadenopathy, with mitotic index lower than five mitosis per HPF.…”

“…The disease is more common in the stomach and in individuals who are over 50 years old, with average age varying between 55 and 67 (29,31) . Clinical manifestations are unspecific and depend on the lesion site.…”

“…Other characteristics can still be found especially in tumors of high histological degree, such as mucosa ulceration (3%-88%), cavitation and areas of central hypodensity (20%-49%) which can correspond to cystic degeneration, hemorrhage or necrosis (9,16,23,29,32) . Presence of gas or contrast in the interior of the lesion can suggest presence of mucosa ulceration and fistula formation (18) .…”

“…Metastatic potential seems to be related to the expression of the immunohistochemistry marker CD34 (25) , being the liver and the peritoneum the most common sites of occurrence (29) . In the present study, we found seven (33.3%) patients with invasion of adjacent organs, 57.2% of them presented high mitotic index and only 1 (4.8%) patient with hepatic metastasis, also presenting mitotic index superior to five mitosis per HPF.…”

Emergency surgery for hemorrhagic shock caused by a gastrointestinal stromal tumor of the ileum: A case report

“…In the present case, the patient developed hemorrhagic shock; thus, upper endoscopy, colonoscopy, abdominal contrast-enhanced CT, and DBE were performed to investigate the source of the hemorrhage. Abdominal CT plays an important role in the diagnosis of small intestinal GISTs, particularly contrast-enhanced CT in cases with excessive bleeding (6,7). In the present case, abdominal contrast-enhanced CT revealed that the hemorrhagic source was the small intestine, although no tumor was detected.…”